1. Field of the Invention
The present invention relates to a motor control system.
2. Description of Related Art
Previously, a protective device, such as a bimetal or a PTC thermistor, is provided in a housing of a motor to protect the motor from burnout. When the motor generates an abnormally high heat, the protective device shuts down an electric circuit to stop supply of the electric power to the motor.
When the protective device is provided to the motor, a size of the motor is disadvantageously increased to cause an increase in a size of the entire system. Thus, in a motor control system, which is disclosed in Japanese Unexamined Patent Publication No. H11-164472, the above protective device is not provided, and a control apparatus, which controls an operation of the motor, computes an estimated temperature of the motor based on a voltage applied to the motor and an application time for applying the voltage to the motor in view of a previously estimated temperature value.
In a vehicle, various electric devices are installed, so that a load of a vehicle battery, which supplies the electric power to these devices, is relatively high. Therefore, there is an increasing demand for reducing the power consumption of these electric devices installed in the vehicle.
However, in the motor control system, which computes the estimated temperature of the motor, the accurate estimated temperature is required at the time of restarting the motor even after turning off of the ignition switch upon stopping of the motor. Thus, the computing operation for computing the estimated temperature needs to be continuously performed. Thus, even though the motor is stopped, a microcomputer of the motor control system needs to continuously perform the computing operation of the estimated temperature and thereby always consumes the electric power of the vehicle battery.